REISS A. PEREZ

BSMT 3L

REISS A. PEREZ

MuscularTissue:-D

REISS A. PEREZ

Tissues are groups of cells that are similar in structure and function.

* EpitheliumCoveringsLinings of surfaces

* ConnectiveSupportBone, ligaments, fat

* MuscleMovement

* NervousControlBrain, nerves, spinal

cord

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•Muscle – a Latin word for “little mouse”•Muscle is the primary tissue in the

•Heart (cardiac MT)•Walls of hollow organs (Smooth MT)

•Skeletal muscle•Makes up nearly half the body’s mass

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Functions of muscle tissueContractility

Long cells shorten and generate pulling force

ExcitabilityElectrical nerve impulse stimulates the muscle cell to contract

ExtensibilityCan be stretched back to its original length by contraction of an opposing muscle

ElasticityCan recoil after being stretched

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Location Function Appearance Control

Skeletalskeleton

movement,

heat, posture

striated, multi-

nucleated

(eccentric), fibers

parallel

voluntary

Cardiacheart

pump blood

continuously

striated, one

central nucleusinvoluntary

Visceral

(smooth

muscle)

G.I. tract,

uterus, eye,

blood

vessels

Peristalsis,

blood

pressure,

pupil size,

erects hairs

no striations, one

central nucleusinvoluntary

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REISS A. PEREZ

REISS A. PEREZ

REISS A. PEREZ

REISS A. PEREZ

NervousTissue:-D

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•Nervous tissue comprises the nervous system.•Nervous tissue includes:

•Nerve cells:•Neurons. •Supportive cells:

•Schwann cells in peripheral nervous system (P.N.S) •Glial cells in central nervous system (C.N.S)

•Nerve fibers.•Nerve endings:

•Receptors or sensory nerve endings.•Effectors or motor nerve endings.

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The neuron is the structural and functional unit of the nervous system. •The neuron has 2 highly developed physiologic properties:

•Irritability, is the capacity to generate nerve impulses in response to various stimuli.•Conductivity, is the ability to transmit the impulses along the processes of the neuron.

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Fine structure of neuron•The cell body of the neuron contains: •Central euchromatic vesicular nucleus (open-face nucleus).•Perinuclear very well developed Golgi Complex.•Mitochondria (are found throughout the neuron i.e. in cell body and its processes).•Rough Endoplasmic reticulum (rER) is present only in cell body and dendrites and not present in the axon or axon hillock. RER appears as clumps of basophilic material called Nissl granules. •Neurofibrils (are distributed throughout the neuron and appear by light microscope).•Microtubules are found all over the neuron.•Inclusions found in nerve cells include:

•a) fat droplets•b) pigments as lipofuscin, melanin•c) glycogen present only in embryonic neurons, but in adult neurons it is absent because it depends on oxidative metabolism. Therefore nervous system is vulnerable (sensitive) to anoxia.

•N.B.:•Centrioles are not found in mature neurons, so they are incapable of cell division.

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Processes of the neuron: They are the axon and the dendrites.

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•The axon (axis cylinder):•It is the efferent process of the neuron which carries the impulse away from the cell body. •It originate from the cell body by a conical portion called “axon hillock”.•It is a single, thin, long process with uniform size.•It gives some collateral branches and many terminal branches.•It is surrounded with a membrane called axolemma and its cytoplasm is called axoplasm.•It contains mitochondria, microtubules and neurofibrils.•It does not contain Nissl granules. •As the axon is devoid of rER, it depends on the proteins synthesized in the cell body which is conveyed by the aid of the movements of microtubules throughout the axon by a process called axoplasmic transport.

•The Dendrites:•They are the afferent processes of the neuron which carry the impulse to the neuron.•They are multiple, short, thick processes and their thickness decreases towards its end.•They have many branches with spines.•They contain mitochondria, microtubules and neurofibrils.•They contain Nissl granules.

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REISS A. PEREZ

Types of the neurons: are classified according to number of processes into:•Pseudo-unipolar neurons: which have single process, then divides into axon and dendrite. They are present in dorsal root ganglion (also called spinal ganglion or sensory ganglion).•Bipolar neurons: they are spindle-shaped with 2 processes; one axon and one dendrite. They are present in areas of special sensations as: retina, olfactory mucosa and inner ear.•Multipolar neurons: they have several processes, the nerve cell body takes several shapes as follows:

•Pyramidal cells: as in cerebral cortex.•Purkinje (flask-shaped) cells; as in cerebellar cortex.•Stellate cells: as in

•Gray matter of spinal cord (anterior horn cells).•Autonomic ganglia.

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REISS A. PEREZ

Types of nerve fibers:•In CNS, all the fibers have no neurilemma sheath and may be:

•Non-myelinated (naked): as in grey matter.•Myelinated: as in white matter.

•In PNS, all the fibers (except the nerve endings) have neurilemma sheath and may be:

•Non-myelinated: as post-ganglionic sympathetic fibers. •Myelinated: as all the peripheral nerves.

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Schwan cells (neurolemmal cells)•These cells surround the axons of peripheral nerves. They look like tubes which envelop the axon. They have peripheral oval nucleus and basophilic cytoplasm.• Whether the nerve fiber is myelinated or not, it is related to Schwann cells.

•If the axon is myelinated, one Schwann cell is related to each axon.•In non-myelinated axons, one Schwann cell is related to several axons.

•Functions of Schwann cells:•They have a protective and a metabolic role for the axons.•They act as an insulator for the nerve impulse.•They are essential for regeneration of injured peripheral neurons.•They form myelin sheath which is important because:

•It insulates the nerve impulse.•It increases the conduction velocity of the axon.

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GangliaGanglia are either:

•Autonomic ganglia (sympathetic & parasympathetic)•Spinal (sensory) ganglia.

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Satellite Cells: form a layer around ganglion cells and separate them from blood capillaries. It helps metabolic exchange between ganglion cells and

blood.

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Spinal (sensory) ganglion Autonomic GanglionSurrounded by thick connective tissue capsule.

Surrounded by thin connective tissue capsule.

Cells are round or oval (pseudo-unipolar)

Cells are stellate (multipolar)

Cells are arranged in groups Cells are scattered

Cells are not of same size Of equal small size

Few number of cells Large number of cells

Cells with central nuclei Cells with peripheral nuclei

Myelinated nerve fibres separate the groups of cells

Unmyelinated nerve fibres separate the cells

Cells are surrounded by many satellite cells

Few satellite cells

No synapse between neurons Has synapses between neurons

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Neuroglia•Neuroglial cells are the supporting cells within the CNS. They have a function similar to Schwann cells in PNS. They have many types:•Astrocytes: these cells support the neurons. They are either fibrous or protoplasmic.

•Fibrous astrocytes: With long processes which branch infrequently. They are found in white matter. They have euchromatic nuclei and a vascular pedicle, i.e. one process ends on a small blood vessel. Their cytoplasm contains neuroglial fibers.•Protoplasmic astrocytes: With short processes. They are found in gray matter. Their cytoplasm is rich in cytoplasmic granules called gliosomes which are considered as lysosomes.

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Oligodendrocytes:

With few processes, (dark) nuclei, and contain many

microtubules. It is responsible for myelin

formation in CNS by sending processes to

several axons.

Microglial cells:

– Small in size with few processes and elongated dark nucleus. Function: phagocytosis.

REISS A. PEREZ

REISS A. PEREZ

REISS A. PEREZ

THANK YOU MAM ALMOND :-D